In a diagnostic process of infectious and hereditary diseases, molecular detection (such as nucleic acid detection) can remarkably shorten a detection window period and improve detection sensitivity. Generally, the quality (such as purity, etc.) of an analyte obtained from a specimen is an important factor which affects a detection result. For the nucleic acid detection, an amount and purity of the nucleic acid extracted from the specimen directly affect a result of the subsequent PCR (polymerase chain reaction) detection.
The nucleic acid is generally extracted through the following steps: 1) pyrolysis of a membrane covering the nucleic acid and release of the nucleic acid; 2) removal of proteins; and 3) collection of the nucleic acid. Classical methods include a boiling pyrolysis method and a phenol-chloroform extraction method. In the boiling pyrolysis method, a precipitant is first added into a sample, and after the centrifuging, a supernatant is removed so as to remove small-molecular inhibitors and precipitate virus particles; and then pyrolysis liquid is added and boiled so as to release DNA and precipitate macromolecular inhibitors such as residual proteins, etc., and centrifuging is performed to obtain the supernatant, i.e., DNA, in the phenol-chloroform extraction method, the pyrolysis liquid is first added into the sample; after chloroform is added, centrifuging is carried out so as to release RNA and enable the RNA to be separated from an albumen layer; and then the supernatant is added into isopropanol so as to extract the RNA; after the centrifuging, the supernatant is removed, and after ethanol is added for washing, the RNA is obtained. Since the two methods are complex in steps and involve in repeated centrifuging or heating, the automation is inconvenient to realize, and the manual labor intensity is high. On this basis, a method for extracting the nucleic acid with a membrane technology exists, which simplifies the operation, and can realize the automation. However, when the membrane is used to wash and collect the nucleic acid, a centrifugal machine is still needed, which is a major limitation of the method.
With the development of the materials science, a nanometer particle (magnetic bead) is used for the nucleic acid extraction process. The paramagnetic nano particle can specifically or non-specifically adsorb the nucleic acid, and can conveniently separate the nucleic acid from a water phase by using a magnetic field, thereby achieving a purpose of extracting the nucleic acid. Once this material is used, it may cause the research and development of the automatic nucleic acid extraction technology. Various automatic nucleic acid extraction technologies and devices based on the nanomagnetic particles emerge. For example, nucleic acid extraction steps specifically include: in a sample containing the nucleic acid, 1) pyrolysis: the pyrolysis liquid is added; after the nucleic acid is pyrolysed from the sample, 2) combination: magnetic beads are added, and the magnetic beads are specifically combined with the nucleic acid; 3) washing: washing liquid is added, impurities such as proteins, etc. on the nucleic acid are removed through the washing step; 4) elution: elution liquid is added to separate the magnetic beads and the nucleic acid; and 5) separation: the magnetic beads are separated and gathered in a magnetic field so as to obtain the purified nucleic acid. However, considerable operation steps correspond to the nucleic extraction steps. Specifically, the pyrolysis liquid, the magnetic beads and the sample are first placed in a beaker (or a sample tube); a magnetic stick (rod-shaped magnet) and a disposable tip sleeved at one end of the magnetic stick are cooperatively placed into the beaker containing the above solution; the magnetic stick and the tip thereof are enabled to slowly move up and down so as to collect combinations of the magnetic heads and the nucleic acid; then the magnetic stick and the tip are collectively transferred into another solution (washing liquid); the magnetic stick is first taken out, so that the magnetic field disappears; and the tip moves up and down rapidly in the washing liquid, so that the combinations of, the magnetic, beads and the nucleic acid enter the solution. Then the magnetic stick is used to collect the combinations of the magnetic, beads, and the nucleic acid after being sleeved with the tip, and the magnetic stick and the tip are separated in the elution liquid. The obtained solution containing the magnetic beads and the nucleic acid is returned into the beaker so as to collect the magnetic beads and to obtain a pure nucleic acid solution.
That is, the cooperative application of the rod-shaped magnet and the disposable tip may transfer the magnetic heads from one reagent to another reagent. In a specific example, the above-mentioned rod-shaped magnets are arranged in an array (2 columns*8 rows, 4 columns*8 rows or 12 columns*8 rows); the disposable tip is arranged in an array of 1*8 or 12*8; and a reaction tube employs a 96-hole deep-hole plate. With respect to a working way, it can be divided into two types: one type is to employ the magnetic stick array of 2*8 or 4*8 and the disposable tip array of and an extraction process of 16 or 32 samples is completed in one deep-hole plate. The other type is to employ the magnetic stick array of 12*8 and the disposable tip array of 12*8; one extraction step (a reagent) is completed in one deep-hole plate; and the whole extraction process is completed collectively by using a plurality of deep-hole plates, and the extraction of 96 samples can be completed at one time.
When the magnetic separation device realizes the full automation of the entire extraction process, the cooperation of a liquid workstation is needed to distribute the sample and the reagent; or the reagent is pre-loaded in the deep-hole plate, and the sample is manually loaded. In addition, the above-mentioned magnetic-pen separation method still his many deficiencies: 1) the processing course of each independent sample is inconvenient to, track. Since a bath processing manner is adopted, a certain number of samples are simultaneously processed at different stages, and the failure of each sample in a batch at each stage cannot be correspondingly responded and processed in the processing course; and 2) in the case that the number of the samples is uncertain, the application efficiency is low, and the optimum performance can be obtained only under the designed processing throughput according to the number of magnetic pens and the design of the corresponding reaction vessels. If the number of the samples is smaller than the designed throughput, consumables may be wasted; and if the number of the samples is greater than the designed throughput, the re-operation is needed.
Another device for nucleic acid extraction using the magnetic bead method is a magnetic separation device carried on a liquid processing workstation. Such magnetic separation device generally consists of a square plate and rod-shaped magnets perpendicular to the plane of the square plate or strip-shaped magnets parallel to the plane in an array of a certain distance. The magnetic separation device can absorb the magnetic particles in each hole of the deep-hole plate onto the side wall, and can inject or transfer the reagent to complete the processing of different reagents by virtue of a liquid transfer mechanical arm of the liquid workstation, thereby completing the nucleic acid extraction process of one sample in a same hole.
Therefore, since all the devices fir nucleic acid extractions using the magnetic bead method in the prior art are manual or semiautomatic devices, the independent processing or the batch processing of the nucleic acid extraction can only be realized. Therefore, a hill-automatic device for nucleic acid extraction using the magnetic bead method needs to be provided in the art, and the device can be used to continuously extract the nucleic acid.